The confinement of phonon propagation in TiAlN/Ag multilayer coatings with anomalously low heat conductivity

TiAlN/Ag multilayer coatings with a different number of bilayers and thicknesses of individual layers were fabricated by DC magnetron co-sputtering. Thermal conductivity was measured in dependence of Ag layer thickness. It was found anomalous low thermal conductivity of silver comparing to TiAlN and Ag bulk standards and TiAlN/TiN multilayers. The physical nature of such thermal barrier properties of the multilayer coatings was explained on the basis of reflection electron energy loss spectroscopy. The analysis shows that nanostructuring of the coating decreases the density of states and velocity of acoustic phonons propagation. At the same time, multiphonon channels of heat propagation degenerate. These results demonstrate that metal-dielectric interfaces in TiAlN/Ag coatings are insurmountable obstacles for acoustic phonons propagation

Interface-Induced Plasmon Nonhomogeneity in Nanostructured Metal-Dielectric Planar Metamaterial

Transformations of the electronic structure in thin silver layers in metal-dielectric (TiAlN/Ag) multilayer nanocomposite were investigated by a set of electron spectroscopy techniques. Localization of the electronic states in the valence band and reduction of electron concentration in the conduction band was observed. This led to decreasing metallic properties of silver in the thin films. A critical layer thickness of 23.5 nm associated with the development of quantum effects was determined by X-ray photoelectron spectroscopy. Scanning Auger electron microscopy of characteristic energy losses provided images of plasmon localization in the Ag layers. The nonuniformity of plasmon intensities distribution near the metal-nitride interfaces was assessed experimentally

Aspect ratio of nano/microstructures determines Staphylococcus aureus adhesion on PET and titanium surfaces

Aims: Joint infections cause premature implant failure. The avoidance of bacterial colonization of implant materials by modification of the material surface is therefore the focus of current research. In this in vitro study the complex interaction of periodic structures on PET and titanium surfaces on the adhesion of Staphylococcus aureus is analysed. Methods and Results: Using direct laser interference patterning as well as roll-to-roll hot embossing methods, structured periodic textures of different spatial distance were produced on surfaces and S. aureus were cultured for 24 h on these. The amount of adhering bacteria was quantified using fluorescence microscopy and the local adhesion behaviour was investigated using scanning electron microscopy. For PET structures, minimal bacterial adhesion was identified for an aspect ratio of about 0·02. On titanium structures, S. aureus adhesion was significantly decreased for profile heights of < 200 nm. Our results show a significantly decreased bacterial adhesion for structures with an aspect ratio range of 0·02 to 0·05. Conclusions: We show that structuring on surfaces can decrease the amount of S. aureus on titanium and PET as common implant materials. Significance and Impact of the Study: The study highlights the immense potential of applying specific structures to implant materials to prevent implant colonization with pathogen bacteria.Fil: Meinshausen, A. K.. Otto-von-Guericke-Universität Magdeburg; AlemaniaFil: Herbster, M.. Otto-von-Guericke-Universität Magdeburg; AlemaniaFil: Zwahr, C.. Technische Universität Dresden; AlemaniaFil: Soldera, Marcos Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; ArgentinaFil: Müller, A.. Otto-von-Guericke-Universität Magdeburg; AlemaniaFil: Halle, T.. Otto-von-Guericke-Universität Magdeburg; AlemaniaFil: Lasagni, A. F.. Technische Universität Dresden; AlemaniaFil: Bertrand, J.. Otto-von-Guericke-Universität Magdeburg; Alemani

Formation of a metastable nanostructured mullite during Plasma Electrolytic Oxidation of aluminium in “soft” regime condition

International audienceThis paper demonstrates the possibility of producing a lamellar ceramic nanocomposite at the topmost surface of oxide coatings grown with the Plasma Electrolytic Oxidation process (PEO). PEO was conducted on aluminium in a silicate-rich electrolyte under the so-called "soft" regime. Nanoscale characterisation showed that the transition from the "arcs" to the "soft" regime was concomitant with the gradual formation of a 1:1 mullite/alumina lamellar nanocomposite (≈120 nm thick) that filled the cavity of the PEO "pancake" structure. Combined with plasma diagnostic techniques, a three-step growth mechanism was proposed: (i) local melting of alumina under the PEO micro-discharges (≈3200 K at high heating rate ≈3 × 10 8 K·s −1); (ii) progressive silicon enrichment of the melt coming from the electrolyte; and (iii) quenching of the melt at a cooling rate of ≈3.3 × 10 7 K·s −1 as the micro-discharge extinguishes. Under such severe cooling conditions, the solidification process was non-equilibrium as predicted by the metastable SiO 2-Al 2 O 3 binary phase diagram. This resulted in phase separation where pure alumina lamellae alternate periodically with 1:1 mullite lamellae

Teste de condutividade elétrica em sementes de Calophyllum brasiliense Cambess (Calophyllaceae).

Edição dos resumos do 18º Congresso Brasileiro de Sementes, 2013, Florianópolis. CD-ROM

Uso do óleo essencial de alfavaca-cravo (Ocimum gratissimum) na água de transporte do tambaqui (Colossoma macropomum) para controle de monogenóides.

O objetivo deste estudo foi avaliar a eficácia do óleo essencial de alfavaca-cravo (Ocimum gratissimum) na água de transporte do tambaqui (Colossoma macropomum) para o controle de helmintos monogenóides

Coarse-Grained Models of Biological Membranes within the Single Chain Mean Field Theory

The Single Chain Mean Field theory is used to simulate the equilibrium structure of phospholipid membranes at the molecular level. Three levels of coarse-graining of DMPC phospholipid surfactants are present: the detailed 44-beads double tails model, the 10-beads double tails model and the minimal 3-beads model. We show that all three models are able to reproduce the essential equilibrium properties of the phospholipid bilayer, while the simplest 3-beads model is the fastest model which can describe adequately the thickness of the layer, the area per lipid and the rigidity of the membrane. The accuracy of the method in description of equilibrium structures of membranes compete with Monte Carlo simulations while the speed of computation and the mean field nature of the approach allows for straightforward applications to systems with great complexity.Comment: Accepted for publication in Soft Matte

Conditioning of hiPSC-derived cardiomyocytes using surface topography obtained with high throughput technology

Surface functionalization of polymers aims to introduce novel properties that favor bioactive responses. We have investigated the possibility of surface functionalization of polyethylene terephthalate (PET) sheets by the combination of laser ablation with hot embossing and the application of such techniques in the field of stem cell research. We investigated the response of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to topography in the low micrometer range. HiPSC-CMs are expected to offer new therapeutic tools for myocardial replacement or regeneration after an infarct or other causes of cardiac tissue loss. However, hiPSC-CMs are phenotypically immature compared to myocytes in the adult myocardium, hampering their clinical application. We aimed to develop and test a high-throughput technique for surface structuring that would improve hiPSC-CMs structural maturation. We used laser ablation with a ps-laser source in combination with nanoimprint lithography to fabricate large areas of homogeneous micron- to submicron line-like pattern with a spatial period of 3 µm on the PET surface. We evaluated cell morphology, alignment, sarcomeric myofibrils assembly, and calcium transients to evaluate phenotypic changes associated with culturing hiPSC-CMs on functionalized PET. Surface functionalization through hot embossing was able to generate, at low cost, low micrometer features on the PET surface that influenced the hiPSC-CMs phenotype, suggesting improved structural and functional maturation. This technique may be relevant for high-throughput technologies that require conditioning of hiPSC-CMs and may be useful for the production of these cells for drug screening and disease modeling applications with lower costs.Fil: Cortella, Lucas R. X.. Universidade de Sao Paulo; BrasilFil: Cestari, Idágene A.. Universidade de Sao Paulo; BrasilFil: Lahuerta, Ricardo D.. Universidade de Sao Paulo; BrasilFil: Arana, Matheus C.. Universidade de Sao Paulo; BrasilFil: Soldera, Marcos Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; ArgentinaFil: Rank, Andreas. Technische Universität Dresden; AlemaniaFil: Lasagni, Andrés F.. Technische Universität Dresden; AlemaniaFil: Cestari, Ismar N.. Universidade de Sao Paulo; Brasi

Uso de drogas psicotrópicas por estudantes: prevalência e fatores sociais associados

OBJECTIVE: To determine the prevalence of the heavy use of drugs among elementary and high school students in a sample of public and private schools, and to identify associated demographic, psychological, cultural and social factors. METHODS: This report describes a cross-sectional study using an intention-type sampling technique that compared public schools in central and peripheral areas and private schools. An anonymous self-administered questionnaire was applied. The sample consisted of 2,287 elementary and high school students in the city of Campinas in 1998. Heavy use of drugs was defined as the use of drugs on 20 or more days during the 30 days preceding the survey (WHO, 1981). For the statistical analysis, polytomic logistic regression analysis (logit model) was utilized to identify factors that influenced this manner of using drugs. RESULTS: Heavy use of legal and illegal drugs was found as follows: alcohol (11.9%), tobacco (11.7%), marijuana (4.4%), solvents (1.8%), cocaine (1.4%), medications (1.1%) and ecstasy (0.7%). The heavy use of drugs was greatest among students at the city-center public school who had daytime jobs and studied in the evenings. These students were in the A and B socioeconomic classes and had had little religious education during childhood. CONCLUSIONS: Greater availability of cash and specific socialization patterns were identified as factors associated with the heavy use of drugs among students.OBJETIVO: Determinar a prevalência do uso pesado de drogas por estudantes de primeiro e segundo graus em uma amostra de escolas públicas e particulares, e identificar fatores demográficos, psicológicos e socioculturais associados. MÉTODOS: Trata-se de um estudo transversal com uma técnica de amostragem do tipo intencional comparando-se escolas públicas de áreas periféricas e centrais e escolas particulares. Foi utilizado um questionário anônimo de autopreenchimento. A amostra foi constituída por 2.287 estudantes de primeiro e segundo graus da cidade de Campinas, SP, no ano de 1998. Considerou-se uso pesado, o uso de drogas em 20 dias ou mais nos 30 dias que antecederam a pesquisa. Para análise estatística, utilizou-se a análise de regressão logística politômica - modelo logito, visando identificar fatores que influenciem este modo de usar drogas. RESULTADOS: O uso pesado de drogas lícitas e ilícitas foi de: álcool (11,9%), tabaco (11,7%), maconha (4,4%), solventes (1,8%), cocaína (1,4%), medicamentos (1,1%), ecstasy (0,7%). O uso pesado foi maior entre os estudantes da escola pública central, do período noturno, que trabalhavam, pertencentes aos níveis socioeconômicos A e B, e cuja educação religiosa na infância foi pouco intensa. CONCLUSÕES: Maior disponibilidade de dinheiro e padrões específicos de socialização foram identificados como fatores associados ao uso pesado de drogas em estudantes